Countries where women are more empowered win more medals and send more athletes to the Summer Olympics, new research in the US has revealed.

The effect of women’s empowerment held for both men and women, although it was stronger for female athletes, according to a study by researchers at Michigan’s Grand Valley State University. The findings were published in April 2014 in the Journal of Sports Economics.

The research, led by Aaron Lowen, associate professor of economics at Grand Valley State, provides evidence for the popular but previously untested hypothesis that women’s empowerment leads to international athletic success.

The authors examined the success of more than 130 nations participating in the Summer Olympics from 1996 through 2012. Similar to previous studies, they found that more populous and wealthier nations were more successful.

However, they also showed that another important predictor of success was the Gender Inequality Index or GII. The GII includes information on women’s reproductive health, political empowerment and participation in the labor force, and it ranges from 0 (no inequality between genders) to 100 (extreme inequality). The authors found that a 10-point decrease in GII was associated with winning about one extra medal for men and 1.5 medals for women. They found similar results when looking at participation and other measures of success, such as medals won per athlete.

The researchers focused on the Summer Olympics because it is the world’s largest elite sports competition in terms of participating individuals and nations and the number of distinct events. The Olympics are also ideal because women’s participation has steadily increased to a level that is almost as high as men’s.

“Many studies have shown that women’s empowerment is linked with economic development and better outcomes for children, but there’s been little research on whether it leads to female sports success,” Lowen said.

“We read claim after claim that it does, so we decided it was worth finding out if it’s true. Fortunately, the results turned out to be clear cut. No matter how we conducted the analyses or what measures of success we used, women’s empowerment predicted Olympic success.”

Besides finding support for the connection between gender equality and Olympic success, there were some unanticipated findings. One was that greater gender equality was also associated with greater success for men, even after controlling other success predictors, such as population and wealth.

“The benefit to male athletes was a surprise, and we don’t really understand why this occurs,” said Lowen. “One idea is that societies that bring women into the workforce generate wealth in ways that are not captured with traditional wealth measures, such as gross domestic product. These societies may afford both men and women greater opportunities for recreational and personal pursuits, including elite athletic training and competition.”

Another unexpected finding was that there was no “Title IX effect” for US women. The well-known federal law prohibits sexual discrimination in educational opportunities, including sports, and has been credited with the success of US women in international competition.

Robert Deaner, associate professor of psychology at Grand Valley State and co-author of the study, said: “Clearly, US women have been remarkably successful in soccer, basketball and many other sports. But once we incorporated other key predictors of Olympic success — population, wealth, and women’s empowerment — we found little evidence that US women are exceptional in comparison to women from other countries or even US men. This doesn’t mean Title IX hasn’t been important for US women — instead it suggests that other countries must have their own means of supporting elite women’s sports.”

The authors stressed there are still outstanding questions, including the direction of causality. “We’ve shown that women’s empowerment and elite athletic success go together, but we can’t say which causes which,” Lowen said.

“To really get at this issue, we’d need some experimental or exogenous change that directly affected one or the other. For instance, if several nations randomly received significant additional resources for women’s sports, we could see if increased women’s empowerment followed, or vice versa. This is obviously a difficult question to answer, but it’s an important one. It might help policy makers decide where to invest their resources.”

The authors of the study were Aaron Lowen, Robert Deaner, and Erika Schmitt, all of Grand Valley State University.